1. Field of the Invention
The present invention relates, generally, to buoyant concrete foundations adapted for supporting a building structure on a body of water and, more especially, to an improved buoyant concrete foundation including positive flotation members as integral components thereof and methods for fabricating such foundations.
2. Description of the Background Art
The use of concrete as a building material for the fabrication of floating structures has become quite popular over the last several decades. Concrete offers many advantages over wood, the historic material of choice in the construction of floating docks, piers, and the like. Perhaps the single most important advantage of concrete lies in its greater service longevity as a consequence of its lesser tendencies for degradation; in fact, not only is concrete stronger than wood, its strength increases upon aging. Concrete offers the further advantage of permitting a structure of substantially unitary design. Accordingly, the use of concrete in the fabrication of all varieties of floating structures is now becoming quite widespread.
Many have proposed the use of concrete for float units employed in the construction of wharf structures. For example, U.S. Pat. No. Re. 24,837 discloses such a floating structure consisting of a plurality of units having a generally rectilinear form. A base member is comprised of an overall rectangular float member having a bottom wall and upstanding side and end walls, divided internally by a plurality of bulkheads to yield a series of chambers. A top wall provides a closure means for each of these units, which are provided with peripheral members for affixing a series of floats in a desired configuration. The buoyancy for the float is achieved by the internal cavities of each unit.
Some have suggested refinements on this overall approach, particularly in response to the potential that water may find its way within the internal chambers and cause a loss of buoyancy of the floats. To this end, various types of buoyant materials have been disposed within internal cavities in flotation units to displace any water which might find a path therein. Exemplary of such approaches may be mentioned the flotation units disclosed in U.S. Pat. Nos. 3,779,192, 3,967,569, and 4,070,980. In general a cellular polymeric foam, such as expanded polystyrene or polyurethane, is disposed substantially completely within a closed chamber, the walls of which comprise the concrete float or buoyant structure.
A somewhat different approach is suggested in U.S. Pat. No. 3,215,108, which discloses a floating structure specifically designed to support a building such as a boathouse on a body of water. That patent describes the use of an expanded polymer such as polystyrene where the same forms a flotation medium through and about which are associated frame members for the foundation.
U.S. Pat. No. 4,252,470 reveals a system for the distribution of a utility service, such as electrical power, telephone and/or water service, throughout a floating pier assembly comprised of a plurality of buoyant concrete float members. Each of the concrete float members is formed in the general shape of a rectangular concrete shell filled with a buoyant material, such as an expanded polymer, and these units are assembled into the overall shape of the desired pier configuration. As respects one element of the buoyant foundation of the present invention, it should be remarked that the buoyant members are formed with different sidewall geometries, including reentrant geometries, which appear to be included in order to provide thickened wall sections of the completely encapsulating concrete shell at places where adjacent members are joined.
A process for fabricating a concrete buoy is disclosed in U.S. Pat. No. 3,622,656. A reinforcing matrix frame, including screen members, is provided to define a form for the walls of the buoy and a cement mixture is applied by a spray technique to that frame. The patentees there strive to provide an on-site, formless molding of a unitary buoy which may include fairly complex geometries.
While many have applied themselves to the task of developing various types of buoyant concrete structures, there is yet to be provided a buoyant concrete foundation which may serve as a support for a wide range of building structures and which is simply and efficiently fabricated with an eye toward this particular aim.